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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="range.reference.ranges.any_range"></a><a class="link" href="any_range.html" title="any_range">any_range</a> |
| </h4></div></div></div> |
| <h6> |
| <a name="range.reference.ranges.any_range.h0"></a> |
| <span class="phrase"><a name="range.reference.ranges.any_range.description"></a></span><a class="link" href="any_range.html#range.reference.ranges.any_range.description">Description</a> |
| </h6> |
| <p> |
| <code class="computeroutput"><span class="identifier">any_range</span></code> is a range that |
| has the type information erased hence a <code class="computeroutput"><span class="identifier">any_range</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_traversal_tag</span><span class="special">,</span> <span class="keyword">int</span><span class="special">,</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">ptrdiff_t</span><span class="special">></span></code> |
| can be used to represent a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code>, a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">list</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code> or many other types. |
| </p> |
| <p> |
| The <a href="http://www.artima.com/cppsource/type_erasure.html" target="_top">type |
| erasure article</a> covers the motivation and goals of type erasure |
| in this context. Clearly my implementation is building upon a lot of prior |
| art created by others. Thomas Becker's <code class="computeroutput"><span class="identifier">any_iterator</span></code> |
| was a strong influence. Adobe also have an <code class="computeroutput"><span class="identifier">any_iterator</span></code> |
| implementation, but this has very tight coupling to other parts of the |
| library that precluded it from use in Boost.Range. Early development versions |
| of this Range Adaptor directly used Thomas Becker's any_iterator implementation. |
| Subsequently I discovered that the heap allocations of this and many other |
| implementations cause poor speed performance particularly at the tails |
| of the distribution. To solve this required a new design that incorporated |
| the embedded buffer optimization. |
| </p> |
| <p> |
| Despite the underlying <code class="computeroutput"><span class="identifier">any_iterator</span></code> |
| being the fastest available implementation, the performance overhead of |
| <code class="computeroutput"><span class="identifier">any_range</span></code> is still appreciable |
| due to the cost of virtual function calls required to implement <code class="computeroutput"><span class="identifier">increment</span></code>, <code class="computeroutput"><span class="identifier">decrement</span></code>, |
| <code class="computeroutput"><span class="identifier">advance</span></code>, <code class="computeroutput"><span class="identifier">equal</span></code> etc. Frequently a better design |
| choice is to convert to a canonical form. |
| </p> |
| <p> |
| Please see the <a class="link" href="../adaptors/reference/type_erased.html" title="type_erased">type_erased</a> |
| for a Range Adaptor that returns <code class="computeroutput"><span class="identifier">any_range</span></code> |
| instances. |
| </p> |
| <h6> |
| <a name="range.reference.ranges.any_range.h1"></a> |
| <span class="phrase"><a name="range.reference.ranges.any_range.synopsis"></a></span><a class="link" href="any_range.html#range.reference.ranges.any_range.synopsis">Synopsis</a> |
| </h6> |
| <p> |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> |
| <span class="keyword">class</span> <span class="identifier">Value</span> |
| <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Traversal</span> |
| <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Reference</span> |
| <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Difference</span> |
| <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Buffer</span> <span class="special">=</span> <span class="identifier">any_iterator_default_buffer</span> |
| <span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">any_range</span> |
| <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">iterator_range</span><span class="special"><</span> |
| <span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">any_iterator</span><span class="special"><</span> |
| <span class="identifier">Value</span> |
| <span class="special">,</span> <span class="identifier">Traversal</span> |
| <span class="special">,</span> <span class="identifier">Reference</span> |
| <span class="special">,</span> <span class="identifier">Difference</span> |
| <span class="special">,</span> <span class="identifier">Buffer</span> |
| <span class="special">></span> |
| <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">any_iterator</span><span class="special"><</span> |
| <span class="identifier">Value</span> |
| <span class="special">,</span> <span class="identifier">Traversal</span> |
| <span class="special">,</span> <span class="identifier">Reference</span> |
| <span class="special">,</span> <span class="identifier">Difference</span> |
| <span class="special">,</span> <span class="identifier">Buffer</span> |
| <span class="special">></span> <span class="identifier">any_iterator_type</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">iterator_range</span><span class="special"><</span><span class="identifier">any_iterator_type</span><span class="special">></span> <span class="identifier">base_type</span><span class="special">;</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">enabler</span> <span class="special">{};</span> |
| <span class="keyword">struct</span> <span class="identifier">disabler</span> <span class="special">{};</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="identifier">any_iterator_type</span> <span class="identifier">iterator</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">any_iterator_type</span> <span class="identifier">const_iterator</span><span class="special">;</span> |
| |
| <span class="identifier">any_range</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">any_range</span><span class="special">&</span> <span class="identifier">other</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">other</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">WrappedRange</span><span class="special">></span> |
| <span class="identifier">any_range</span><span class="special">(</span><span class="identifier">WrappedRange</span><span class="special">&</span> <span class="identifier">wrapped_range</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">),</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">WrappedRange</span><span class="special">></span> |
| <span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">WrappedRange</span><span class="special">&</span> <span class="identifier">wrapped_range</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">),</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">wrapped_range</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span> |
| <span class="keyword">class</span> <span class="identifier">OtherValue</span> |
| <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherTraversal</span> |
| <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherReference</span> |
| <span class="special">,</span> <span class="keyword">class</span> <span class="identifier">OtherDifference</span> |
| <span class="special">></span> |
| <span class="identifier">any_range</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">any_range</span><span class="special"><</span> |
| <span class="identifier">OtherValue</span> |
| <span class="special">,</span> <span class="identifier">OtherTraversal</span> |
| <span class="special">,</span> <span class="identifier">OtherReference</span> |
| <span class="special">,</span> <span class="identifier">OtherDifference</span> |
| <span class="special">,</span> <span class="identifier">Buffer</span> |
| <span class="special">>&</span> <span class="identifier">other</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">other</span><span class="special">),</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">other</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Iterator</span><span class="special">></span> |
| <span class="identifier">any_range</span><span class="special">(</span><span class="identifier">Iterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">Iterator</span> <span class="identifier">last</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">base_type</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| </p> |
| <h6> |
| <a name="range.reference.ranges.any_range.h2"></a> |
| <span class="phrase"><a name="range.reference.ranges.any_range.definition"></a></span><a class="link" href="any_range.html#range.reference.ranges.any_range.definition">Definition</a> |
| </h6> |
| <p> |
| Defined in header file <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">range</span><span class="special">/</span><span class="identifier">any_range</span><span class="special">.</span><span class="identifier">hpp</span></code> |
| </p> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2003-2010 Thorsten Ottosen, |
| Neil Groves<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
| </div></td> |
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